Component for a gas turbine engine with a film hole

ABSTRACT

A component is provided and comprises at least one wall comprising a first and a second surface. At least one film cooling hole extends through the wall between the first and second surfaces and has an outlet region at the second surface. The film cooling hole includes a first expansion section being a side diffusion portion and a second expansion section being a layback diffusion portion, wherein the side diffusion portion is upstream and spaced from the layback diffusion portion.

BACKGROUND OF THE INVENTION

The invention relates generally to gas turbine engines, and, morespecifically, to film cooling therein. In a gas turbine engine, air ispressurized in a compressor and mixed with fuel in a combustor forgenerating hot combustion gases. Energy is extracted from the gases in ahigh pressure turbine (HPT), which powers the compressor, and in a lowpressure turbine (LPT), which powers a fan in a turbofan aircraft engineapplication, or powers an external shaft for marine and industrialapplications.

Engine efficiency increases with temperature of combustion gases.However, the combustion gases heat the various components along theirflowpath, which in turn requires cooling thereof to achieve a longengine lifetime. Typically, the hot gas path components are cooled bybleeding air from the compressor. This cooling process reduces engineefficiency, as the bled air is not used in the combustion process.

Gas turbine engine cooling art is mature and includes numerous patentsfor various aspects of cooling circuits and features in the various hotgas path components. For example, the combustor includes radially outerand inner liners, which require cooling during operation. Turbinenozzles include hollow vanes supported between outer and inner bands,which also require cooling. Turbine rotor blades are hollow andtypically include cooling circuits therein, with the blades beingsurrounded by turbine shrouds, which also require cooling. The hotcombustion gases are discharged through an exhaust which may also belined, and suitably cooled.

In all of these exemplary gas turbine engine components, thin metalwalls of high strength superalloy metals are typically used for enhanceddurability while minimizing the need for cooling thereof. Variouscooling circuits and features are tailored for these individualcomponents in their corresponding environments in the engine. Inaddition, all of these components typically include common rows of filmcooling holes.

A typical film cooling hole is a cylindrical bore inclined at a shallowangle through the heated wall for discharging a film of cooling airalong the external surface of the wall to provide thermal insulationagainst the hot combustion gases which flow thereover during operation.The film is discharged at a shallow angle over the wall outer surface tominimize the likelihood of undesirable blow-off thereof, which wouldlead to flow separation and a loss of the film cooling effectiveness.

Film performance is dictated by effective coverage. If the diffuser istoo aggressive in expansion, it results in the flow stalling and adegree of jetting at the outlet of the diffuser. This jetting isdetrimental as it reduces the effective coverage of the film andintroduces secondary mixing that degrades the film. The side diffusionangle and length govern the physical coverage of the diffuser at theoutlet. The layback diffusion angle governs how the film transitionsfrom the covered diffusion portion to the mainstream flow.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect of the invention, embodiments of the invention relate to acomponent for a gas turbine engine comprising a hot side exposed to ahot air flow, a cool side exposed to a cooling air flow, and a film holepassage extending between the cool side and the hot side wherein aninlet is located on the cool side and an outlet on the hot side. A sidediffusion length is defined by a length between a start of the sidediffusion portion and the outlet. A layback length is defined by alength between a start of the layback diffusion portion and the outlet.In the embodiments the side diffusion length is greater than the laybackdiffusion length.

In another aspect of the invention, embodiments of the invention relateto a film hole passage for a component, with a cool and hot side, of agas turbine engine having an inlet on the cool side, an outlet on thehot, a side diffusion portion, and a layback diffusion portion, whereinthe side diffusion portion is upstream and spaced from the laybackdiffusion portion.

In another aspect of the invention, embodiments of the invention relateto a film hole passage for a component, with a cool and hot side, havingan inlet on the cool side, an outlet on the hot, a side diffusionportion, and a layback diffusion portion, wherein the side diffusionportion is upstream and spaced from the layback diffusion portion, andthe layback diffusion portion defines a layback diffusion length whichis less than 4 times the diameter of a metering section of the filmhole.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic cross-sectional diagram of a gas turbine enginefor an aircraft.

FIG. 2 is a side section view of a combustor and a high pressure turbineof the engine from FIG. 1.

FIG. 3 is a sectional view through a film hole of an engine component ofthe engine from FIG. 1 according to a first embodiment of the invention.

FIG. 4 is a top view of the film hole.

FIG. 5 is FIG. 3 stacked with FIG. 4 and FIG. 6.

FIG. 6 is a bottom view of the film hole.

FIG. 7 is a bottom perspective view of the film hole.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The described embodiments of the present invention are directed to afilm-cooled engine component, particularly in a gas turbine engine. Forpurposes of illustration, aspects of the present invention will bedescribed with respect to an aircraft gas turbine engine. It will beunderstood, however, that the invention is not so limited and may havegeneral applicability in non-aircraft applications, such as other mobileapplications and non-mobile industrial, commercial, and residentialapplications.

FIG. 1 is a schematic cross-sectional diagram of a gas turbine engine 10for an aircraft. The engine 10 has a generally longitudinally extendingaxis or centerline 12 extending forward 14 to aft 16. The engine 10includes, in downstream serial flow relationship, a fan section 18including a fan 20, a compressor section 22 including a booster or lowpressure (LP) compressor 24 and a high pressure (HP) compressor 26, acombustion section 28 including a combustor 30, a turbine section 32including a HP turbine 34, and a LP turbine 36, and an exhaust section38.

The fan section 18 includes a fan casing 40 surrounding the fan 20. Thefan 20 includes a plurality of fan blades 42 disposed radially about thecenterline 12.

The HP compressor 26, the combustor 30, and the HP turbine 34 form acore 44 of the engine 10 which generates combustion gases. The core 44is surrounded by a core casing 46 which can be coupled with the fancasing 40.

A HP shaft or spool 48 disposed coaxially about the centerline 12 of theengine 10 drivingly connects the HP turbine 34 to the HP compressor 26.A LP shaft or spool 50, which is disposed coaxially about the centerline12 of the engine 10 within the larger diameter annular HP spool 48,drivingly connects the LP turbine 36 to the LP compressor 24 and fan 20.

The LP compressor 24 and the HP compressor 26 respectively include aplurality of compressor stages 52, 54, in which a set of compressorblades 56, 58 rotate relative to a corresponding set of staticcompressor vanes 60, 62 (also called a nozzle) to compress or pressurizethe stream of fluid passing through the stage. In a single compressorstage 52, 54, multiple compressor blades 56, 58 may be provided in aring and may extend radially outwardly relative to the centerline 12,from a blade platform to a blade tip, while the corresponding staticcompressor vanes 60, 62 are positioned downstream of and adjacent to therotating blades 56, 58. It is noted that the number of blades, vanes,and compressor stages shown in FIG. 1 were selected for illustrativepurposes only, and that other numbers are possible.

The HP turbine 34 and the LP turbine 36 respectively include a pluralityof turbine stages 64, 66, in which a set of turbine blades 68, 70 arerotated relative to a corresponding set of static turbine vanes 72, 74(also called a nozzle) to extract energy from the stream of fluidpassing through the stage. In a single turbine stage 64, 66, multipleturbine blades 68, 70 may be provided in a ring and may extend radiallyoutwardly relative to the centerline 12, from a blade platform to ablade tip, while the corresponding static turbine vanes 72, 74 arepositioned upstream of and adjacent to the rotating blades 68, 70. It isnoted that the number of blades, vanes, and turbine stages shown in FIG.1 were selected for illustrative purposes only, and that other numbersare possible.

In operation, the rotating fan 20 supplies ambient air to the LPcompressor 24, which then supplies pressurized ambient air to the HPcompressor 26, which further pressurizes the ambient air. Thepressurized air from the HP compressor 26 is mixed with fuel incombustor 30 and ignited, thereby generating combustion gases. Some workis extracted from these gases by the HP turbine 34, which drives the HPcompressor 26. The combustion gases are discharged into the LP turbine36, which extracts additional work to drive the LP compressor 24, andthe exhaust gas is ultimately discharged from the engine 10 via theexhaust section 38. The driving of the LP turbine 36 drives the LP spool50 to rotate the fan 20 and the LP compressor 24.

Some of the ambient air supplied by the fan 20 may bypass the enginecore 44 and be used for cooling of portions, especially hot portions, ofthe engine 10, and/or used to cool or power other aspects of theaircraft. In the context of a turbine engine, the hot portions of theengine are normally downstream of the combustor 30, especially theturbine section 32, with the HP turbine 34 being the hottest portion asit is directly downstream of the combustion section 28. Other sources ofcooling fluid may be, but is not limited to, fluid discharged from theLP compressor 24 or the HP compressor 26.

FIG. 2 is a side section view of the combustor 30 and HP turbine 34 ofthe engine 10 from FIG. 1. The combustor 30 includes a deflector 76 anda combustor liner 77. Adjacent to the turbine blade 68 of the turbine 34in the axial direction are sets of radially-spaced, static turbine vanes72, with adjacent vanes 72 forming nozzles therebetween. The nozzlesturn combustion gas to better flow into the rotating blades so that themaximum energy may be extracted by the turbine 34. A cooling air flow Cpasses through the vanes 72 to cool the vanes 72 as hot air flow Hpasses along the exterior of the vanes 72. A shroud assembly 78 isadjacent to the rotating blade 68 to minimize flow loss in the turbine34. Similar shroud assemblies can also be associated with the LP turbine36, the LP compressor 24, or the HP compressor 26.

One or more of the engine components of the engine 10 includes afilm-cooled substrate in which a film cooling hole, or film hole, of anembodiment disclosed further herein may be provided. Some non-limitingexamples of the engine component having a film-cooled substrate caninclude the blades 68, 70, vanes or nozzles 72, 74, combustor deflector76, combustor liner 77, or shroud assembly 78, described in FIGS. 1-2.Other non-limiting examples where film cooling is used include turbinetransition ducts and exhaust nozzles.

FIG. 3 is a schematic, sectional view showing a portion of an enginecomponent 80 according to an embodiment of the invention. The enginecomponent 80 may be an engine component of the engine 10 from FIG. 1,and can be disposed in a flow of hot gas represented by arrow H. Acooling air flow, represented by arrow C may be supplied to cool theengine component. As discussed above with respect to FIGS. 1-2, in thecontext of a turbine engine, the cooling air can be ambient air suppliedby the fan 20 which bypasses the engine core 44, air from the LPcompressor 24, or air from the HP compressor 26.

The engine component 80 includes a substrate 82 having a first surfacebeing a hot side 84 facing the hot air flow H and a second surface beinga cool side 86 facing the cooling fluid C. The substrate 82 may form awall of the engine component 80; the wall may be an exterior or interiorwall of the engine component 80. The first engine component 80 candefine at least one interior cavity 88 comprising the cool side 86. Thehot side 84 may be an exterior surface of the engine component 80. Inthe case of a gas turbine engine, the hot side 84 may be exposed togases having temperatures in the range of 1000° C. to 2000° C. Suitablematerials for the substrate 82 include, but are not limited to, steel,refractory metals such as titanium, or superalloys based on nickel,cobalt, or iron, and ceramic matrix composites. The superalloys caninclude those in equi-axed, directionally solidified, and single crystalstructures.

The engine component 80 further includes one or more film hole(s) 90extending through the substrate 82 that provide fluid communicationbetween the interior cavity and the hot side 84 of the engine component80. During operation, the cooling air flow C is supplied to the interiorcavity 88 and out of the film hole 90 to create a thin layer or film ofcool air on the hot side 84, protecting it from the hot air flow H.While only one film hole 90 is shown in FIG. 3, it is understood thatthe engine component 80 may be provided with multiple film holes 90,which be arranged in any desired configuration on the engine component80.

It is noted that, in any of the embodiments discussed herein, althoughthe substrate 82 is shown as being generally planar, it is understoodthat that the substrate 82 may be curved for many engine components 80.However, the curvature of the substrate 82 may be slight in comparisonto the size of the film hole 90, and so for the purposes of discussionand illustration, the substrate 82 is shown as planar. Whether thesubstrate 82 is planar or curved local to the film hole 90, the hot andcool sides 84, 86 may be parallel to each other as shown herein, or maylie in non-parallel planes.

The film hole 90 can have an inlet 92 provided on the cool side 86 ofthe substrate 82, an outlet region comprising an outlet 94 provided onthe hot side 84, and a film hole passage 96 connecting the inlet 92 andthe outlet 94. The film hole passage 96 can include a metering section98 for metering of the mass flow rate of the cooling air flow C, and adiffusing section 100 in which the cooling fluid C is expanded to form awider and slower cooling film on the hot side 84. The metering section98 can be a portion of the film hole passage 96 with the smallestcross-sectional area perpendicular to the direction of cooling air flowC through the film hole passage 96. The metering section 98 may be adiscrete location at which the film hole passage 96 has the smallestcross-sectional area, or an elongated section of the film hole passage96. The diffusing section 100 is downstream of the metering section 98with respect to the direction of cooling air flow C through the filmhole passage 96. The diffusing section 100 may be in serial flowcommunication with the metering section 98. The metering section 98 canbe provided at or near the inlet 92, while the diffusing section 100 canbe defined at or near the outlet 94. In most implementations, thediffusing section 100 defines the outlet 94.

The cooling air flow C through the film hole passage 96 is along thelongitudinal axis of the film hole passage 96, also referred to hereinas the centerline 102, which passes through the geometric center of thecross-sectional area of the metering section 98. The film hole 90 can beinclined in a downstream direction of cooling air flow C through thefilm hole passage 96 such that the centerline 102 is non-orthogonal tothe hot and cool sides 84, 86. Alternatively, the film hole 90 may havea centerline 102 that is orthogonal to one or both of the hot and coolsides 84, 86 in the localized area of the substrate 82 through which thecenterline 102 passes. In other embodiments, the centerline 102 of thefilm hole 90 may not be oriented in the direction of the hot air flow H,such that the vector of the cooling air flow C differs from that of thehot air flow H. For example, a film hole that has a compound angledefines a cooling flow vector that differs from the hot air flow vectornot only in cross section, but also in the top-down view looking at thehot side 84.

In the embodiment of FIG. 3, D is the metering diameter defined by themetering section 98 of the film hole 90. The metering section 98 isgenerally circular in cross-section and has a diameter less than 0.48inches. However the specific cross-sectional shape of the meteringsection 98 may differ for other embodiments of the invention; forexample, the cross-sectional shape of the metering section 98 may berectangular or elliptical. For non-circular metering sections 98, themetering diameter D may be the hydraulic diameter of the cross-section,which is defined commonly as four times the cross-sectional area dividedby the cross-sectional perimeter. For very irregular metering sections98 that still are generally circular, such as those commonly produced bypercussion laser machining, the metering diameter D may be the diameterof the largest circular pin that can be passed through the meteringsection 98 without damage. For non-circular sections that also haveirregular surfaces, the metering diameter D may be the hydraulicdiameter of the appropriately shaped largest pin that can be passedthrough without damage. For non-straight or non-constant cross sectionlengths prior to the diffusion section 100, the same overall definitionsmay be used at the minimum cross sectional area location.

The outlet 94 includes an upstream edge 104 and a downstream edge 106 atwhich the film hole passage 96 intersects the hot side 84 of thesubstrate 82. The edges 104, 106 can generally be defined relative tothe direction of the hot air flow H, with the hot air flow H generallydefining an upstream direction 108 and a downstream direction 110relative to the hot side 84, i.e. past the outlet 94. The upstream edge104 generally faces the downstream direction 110 and the downstream edge106 generally faces the upstream direction 108.

In the embodiment of FIGS. 4-6, which illustrate the void defined by thefilm hole 90 of FIG. 3, the diffusing portion 100 further comprises aside diffusion portion 112 and a layback diffusion portion 116. The sidediffusion portion 112 is upstream relative to the outlet 94 and spacedfrom the layback diffusion portion 116. Spaced meaning that the twodiffusion portions begin at different points within the film holepassage 96 with the side diffusion portion 112 beginning upstream 108 ofthe layback diffusion portion 116. The side diffusion portion 112 beginswhere the metering section 98 ends defining a start 114 of the sidediffusion portion 112 and ends at the outlet 94.

The side diffusion portion 112 further defines a side diffusion lengthL_(α) running parallel to the centerline 102 from the start 114 to theupstream edge 104. The side diffusion portion 112 further defines a sidediffusion angle α which expands from the start 114 at a shallow anglemeasured from the centerline 102 and terminating at the outlet 94. Insome embodiments, the side diffusion angle α is less than 12.5 degrees.

The layback diffusion portion 116 begins at a point downstream of thestart 114 of the side diffusion portion 112 but upstream of the outlet94. The layback diffusion portion ends at the outlet 94. The laybackdiffusion portion 116 further defines a layback diffusion length L_(β)running parallel to the centerline 102 from the second start 118 to theupstream edge 104 with the upstream edge being positioned downstream ofthe second start 118. The side diffusion length L_(α) is greater thanthe layback length L_(β) and less than 35 times the diameter D. In someembodiments the layback length L_(β) is less than 4 times the diameter Dor zero, and more particularly less than 3. In some further embodimentsthe layback length L_(β) can be less than zero as measured from thesecond start 118 to the upstream edge 104 with the upstream edge 104being positioned upstream of the second start 118, having a length of upto −0.5 D.

The layback diffusion portion 116 further defines a layback diffusionangle β which expands from the second start 118 towards the cool side 86at a shallow angle measured from the centerline 102 and terminating atthe downstream edge 106. In some embodiments, the layback diffusionangle β is less than 12 degrees.

In these embodiments the intentional spacing between the side diffusionangle α in relationship to the layback diffusion angle β results indeeper plunge depths and coverage for similar diffusion area ratios.This enables more stable diffusion to get the coverage required forimproved film performance which is dictated by effective coverage.

Typical film holes couple the side diffusion angle and layback diffusionangle at the same location. This limits the layback diffusion lengththat the film holes can perform due to the high area ratios that onegets with layback. Separating the layback diffusion angle from the sidediffusion angle allows for more stable diffusion with long sidediffusion length resulting in more coverage. Including the laybackdiffusion angle after the side diffusion angle allows the film totransition to an effectively lower surface angle before meeting the freestream flow.

Separating side diffusion and layback diffusion locations results inlower area ratios for the same coverage and more stable diffusion. Thisalso allows for lower surface angle placement due to less cavityinterference. Both of these result in significant improvement to filmperformance. This higher film effectiveness translates directly toeither durability (increased time on wing) or reduced cooling flow(increased thermal efficiency).

The superior performance of the proposed invention is further driven byreduced mixing between hot gas and coolant at the breakout of the filmhole, which is a direct consequence of L_(β)<L_(α—)alpha. This conditionallows sufficient coverage and lateral spreading of the film to beachieved via large L_(α), while constraining the exit of the hole in thedimension normal to the exit surface by having a short L_(β). The lattercircumstance limits the turbulent length scales and consequent mixing atthe hole exit.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A component for a gas turbine engine comprising:a hot side exposed to a hot air flow; a cool side exposed to a coolingair flow; a film hole passage extending between the cool side and thehot side with an inlet on the cool side and an outlet on the hot side,the film hole passage defining a diameter, the film hole passage furtherdefining a side diffusion portion defining a side diffusion lengthbetween a start of the side diffusion portion and the outlet, and alayback diffusion portion defining a layback diffusion length between astart of the layback diffusion portion and the outlet, wherein the sidediffusion length is greater than the layback diffusion length and thelayback diffusion portion begins at a point upstream of the outlet. 2.The component of claim 1 wherein the side diffusion portion is upstreamand spaced from the layback diffusion portion.
 3. The component of claim1 wherein the side diffusion portion defines a side diffusion angle, α,relative to a centerline for the film hole passage, and the sidediffusion angle is less than 12.5 degrees.
 4. The component of claim 3wherein the layback diffusion portion defines a layback diffusion angle,β, relative to a centerline for the film hole passage, and the laybackdiffusion angle is less than 12 degrees.
 5. The component of claim 4wherein the layback diffusion length is less than 4 times the diameter.6. The component of claim 4 wherein the layback diffusion length is lessthan four times the diameter and the side diffusion length is less than35 times the diameter.
 7. The component of claim 6 wherein the film holepassage has a diameter less than 0.48 inches.
 8. A film hole passage fora component, with a cool and hot side, of a gas turbine engine having aninlet on the cool side, an outlet on the hot, a side diffusion portion,and a layback diffusion portion, wherein the side diffusion portion isupstream and spaced from the layback diffusion portion and the laybackdiffusion portion begins at a point upstream of the outlet.
 9. The filmhole passage of claim 8 wherein the side diffusion portion defines aside diffusion angle, α, relative to a centerline for the film holepassage, and the side diffusion angle is less than 12.5 degrees.
 10. Thefilm hole passage of claim 8 wherein the layback diffusion portiondefines a layback diffusion angle, β, relative to a centerline for thefilm hole passage, and the layback diffusion angle is less than 12degrees.
 11. The film hole passage of claim 8 wherein the side diffusionportion defines a side diffusion length, the layback diffusion portiondefines a layback diffusion length, and side diffusion length is greaterthan then layback diffusion length.
 12. The film hole passage of claim11 wherein the layback diffusion length is less than 4 times a diameterof the film hole passage.
 13. The film hole passage of claim 12 whereinthe layback diffusion length is less than 4 times the diameter and theside diffusion length is less than 35 times the diameter.
 14. The filmhole passage of claim 13 wherein the film hole passage has a diameterless than 0.48 inches.
 15. The film hole passage of claim 8 wherein thefilm hole has the following geometry: a) the side diffusion portiondefines a side diffusion angle, α, relative to a centerline for the filmhole passage, and the side diffusion angle is less than 12.5 degrees, b)the layback diffusion portion defines a layback diffusion angle, β,relative to the centerline for the film hole passage, and the laybackdiffusion angle is less than 12 degrees, and c) wherein the sidediffusion portion defines a side diffusion length, the layback diffusionportion defines a layback diffusion length, and side diffusion length isgreater than then layback diffusion length.
 16. A film hole passage fora component, with a cool and hot side, having an inlet on the cool side,an outlet on the hot, a side diffusion portion, and a layback diffusionportion, wherein the side diffusion portion is upstream and spaced fromthe layback diffusion portion, and the layback diffusion portion definesa layback diffusion length which is less than 4 times a diameter of thefilm hole passage and the layback diffusion portion begins at a pointupstream of the outlet.
 17. The film hole passage of claim 16 whereinthe film hole has the following geometry: a) the side diffusion portiondefines a side diffusion angle, α, relative to a centerline for the filmhole passage, and the side diffusion angle is less than 12 degrees, b)the layback diffusion portion defines a layback diffusion angle, β,relative to the centerline for the film hole passage, and the laybackdiffusion angle is less than 12.5 degrees, and c) wherein the sidediffusion portion defines a side diffusion length, the layback diffusionportion defines a layback diffusion length, and side diffusion length isgreater than then layback diffusion length.
 18. The film hole passage ofclaim 17 wherein the layback diffusion length is less than 4 times thediameter and the side diffusion length is less than 35 times thediameter.